Liquid resin composition which cure upon irradiation with high energy radiation have many important advantages. Since they may be cured within a few seconds without heating, they may be applied on thermally deformable substrates and do not require large equipment for curing. Since they are usually free from any volatile solvent and utilize electric energy for curing, they do not evolve harmful pollutants to the environment. When they are used as a photosensitive material, a high quality image may be reproduced by using short wavelength radiation. Consequently, they find a wide variety of uses in the coating, electronic, printing and other industry as UV or electron beam curable coating compositions, photoresists, electron beam resists, X-ray resists, printing plate making materials and the like.
As is well-known, these radiation curable compositions are normally liquid prior to curing without using any volatile solvent in order that steps for removing solvent and setting the applied composition may be obviated. However, they have to possess a suitable viscosity level to impart them with desired workability without using such volatile solvent. This prevents prior art radiation curable compositions from being applied in greater film thicknesses in a single coating operation. This is because the conventional compositions tend to run with the increase in the amount applied per unit area. The run property may be improved by the incorporation of fine silica particles or various body pigments. The addition of these inorganic fillers, however, tends to adversely affect the weather resistance, appearance or other physical properties of the resulting film. Besides, these inorganic particles tend to cause absorption or scattering of radiation applied because of the difference in refractive index, particle size distribution and chemical constitution between the inorganic particles and the matrix resin. This can result in uneven dose of high energy radiation which, in turn, may produce insufficiently cured portions or curing may take place in undesired areas.